Trunk circuit monitoring signal



Aug- 3, 1954 w w. PHARls TRUNK CIRCUIT MONITORING SIGNAL Filed Oct. s, 1952 EAK lllll INVENTOR. WILLIAM W. PHRS ATTORNEY v Patented ug. 3, 1954 TRUNK CIRCUIT MONITORING- SIGNAL 1-Wriliam W. "Pharis, Rochester, N. Y., 'ass'ignor to "1Stron'1berg--Carlson Company, afeorporation of 'fNewlYork .-Applicationctober 8, 1952,V Serial No.31'3,667

3 Claims. J1

'Thepresent inventionrelatesto telephone systemsand more,particularlmtotrunk circuits h'avlingjimproved monitor` signal arrangements toin- .dicate'lthe operative .condition of vthe circuit.

j Modern telephone exchanges temploynons'id- .erableamounts lof relatively .complex equipment and included ,with i the .equipment are Various indiizi'dually .selectable circuitssuch as selector circuits, ..connector,circuits, and' trunk circuits which have diirerent conditions of operation, In the Caseof Ia trunk circuitwhich, .for example, may "be used ...toprovlide .an .outgoing dial to dial connection Vfrom a selector to a trunk line, the .circuit may have three conditions ofoperatiOn, i. e., rseizcdduring dial p ulse transmission, a talking condition, andreleased. 'In supervisingthe operationofa telephone exchange embodying `such equipment it .is often .desirable .to lbe informed .of the `operative condition of the various cir- -cutssuch asthe trunk .circuitmentioned above.

Itis an object vof lthe presentinvention to provide a trunk circuitv having a monitor signalling `.systemivlfiich will Vindicate in a simple and direct manner the voperative,condition of the trunk circuit, i. e., seized, talking, or released.

.A'featureof theinvention is the provision of a signal .lamp anda control circuit therefor fin association Witha trunk circuit and operative'to ing in .which the solegure is a kcircuit diagram o'f a 'simplied form of trunk vcircuit embodying 'the monitor Alamp signal arrangement.

Referring lto the drawing, the trunk lcircuit is 'connected Ybetween the incoming tip, ring and Isleeve'fcondu'ctors T, R and S, respectively, ,and the outgoing Strunk line conductors TI and Rl. In thedescription yof, the invention, the power 'supply for? energizing ith'e yarious .relays and 'the itive symbols .arezemployed lto :show :the respective connections @to the 'power supply.'l As .eis :customary in ithe art, the :positive :terminal of the .usual 'battery l,power `supply l:(not fshovvn) is A.connected eto ground Tand, will 2be referred xtohereina-fter as fground, rrWhereas ithemegatiye Vterminal of fthe @power supply will be .referred :to faszbattery. 1 It should also :be aunderstcodztlrat .theincoming tip and :ring conductorsmmearrangedito sbeiconnected to a calling line loop circuit (not shown) for lbridge relay .calling .bridge relay winding vThe operation of the calling 'bridge "relay /lfli' 2 seizing the trunk circuit .and that the outgoing trunkline tip and ring conductors, Ti and Rl., are arranged to be connected in 'a reverse batterycalledlineloop .circuit when the calledp'arty answers and the extension Vof the call is thus'c'om- 4,pleted.

closes `contacts lfii and M2 ofthe outgoingtip .and ring conductors, respectively, Vand'colinccts ground at .operated contacts M3 lto energizethe release delayrelay'itii. 'Atthesame time, ground is connected'throughoperated contacts Id3to'the high-resistance Winding liiiAjof thejsupervisory relay HQ which, however, does not loperate at thisjtime since the-current through'the high-'resistance Winding 4is 'notsufcient -to cause such operation. It should be mentioned that the'supervisory'reley Nil yis'provided with differentially Vconnected windings I I DA-and l liiBand the Winding i IGB*isenergizedover-conductors Tl and RI witha polarity opposite to the energization of Winding 116A until the called party VansWersand reverse battery supervision becomes -eective to reversethe polarity'in winding l'i'iB and Aoperate relay im Yas will be later described.

yAccor-'ding to the invention, the monitor signal lamp liti] is connected from battery through-nor- "mally closedcontacts i iii-to Ynormally open contacts vi3i which are operated-by the operation of the release delay relay 36 upon seizure-ofthe trunk circuit and the aforementioned operation of the calling bridge relay M6. With the frevlease -delay relay i3@ operated land contacts 5113i! fclosed, the monitor lamp L |10 is energized from .ground throughoperated contacts i3d, .normal .contacts-iii@ Vto battery, and .is .therebybrig'htly illuminated .to indicate seizure of the atrunk circuit.

The atorementionedoperation of release zdelay y'relay i3@ connects ground at operated'contacts i532 :toth'einconiing sleeve conductor S to mark this trunk circuit fbusy, as is well known. The operation of release delay :relay i3@ throughop- VVerated contacts i333 and normally closed lcontacts -Hll Vestablishes a circuit 'to energize the slow `Ire- Alease kshunt relay VE26 -When the calling -bridge relayfil-ilit :releases on thel rst -dial .impulse-torestorecontacts -l'ft to norm-al. shunt relay flzii,

@being-slow `.to release, remains operated during transmission of dial impulses. The operation of shunt relay closes contacts |2| and |22 and opens contacts |23 and |24 to connect ground through resistance R4 to the outgoing trunk line ring conductor R| and battery through the resistance R3 to the outgoing trunk line tip conductor Tl. During the meshing of the contacts of the shunt relay |20, contacts |25 are closed and contacts |26 are open to momentarily short circuit repeat coil windings |03 and |64, and prevent any inadvertent operation of the supervisory relay ||B due to an accidental energizing oi the relay coil llilB by the battery and ground connection through the resistors R3 and Rd.

With the seizure of the trunk circuit and the operation of the relays |28, |30 and |40, respectively, battery and ground dial pulsing may be transmitted to the remote equipment over the trunk line conductors Ti and Rl by the periodic restoration of the calling bridge relay Mii in response to the dial impulses, as is well known in the art. During pulsing of the calling bridge relay ldil, the release delay relay and slow release shunt relay |23 are periodically and alternately energized to remain operated during the impulsing cycle. At the end of the dial impulses the calling bridge relay It) is again operated to maintain the operation of the release delay relay |30. However, the slow release shunt relay |20 is restored since ground is no longer connected thereto in view of the operated position of contacts |43. With shunt relay |251 restored, the trunk line tip and ring conductors Tl and RI are again connected through operated contacts IM and 42 and normal contacts |23 and |24 to the windings W3 and ill of the repeat coil INDlt It will be noted that talking condensers C! and C2 are provided across which the winding MGA of the calling bridge relay and the winding IBB of the supervisory relay are connected, respectively.

When the extension of the call is thus completed and the calling party answers, the talking battery connections over conductors T| and Rl to winding IWB of the supervisory relay lll) are reversed, and relay Ill therefore operates to open contacts and ||2 and close contacts ||5 and IIB to reverse talking battery from the calling bridge relay to the incoming tip ring conductors T and R. The operation of the supervisory relay Htl also opens contacts H3 and closes contacts to change the energization circuit or" the monitor lamp Llil to be thereafter energized from ground through the series resistor RI. Thus, in such manner, the monitor lamp Lm is energized to provide dim illumination and indicate that the trunk circuit is now in talking condition.

When the called Darty hangs up, the differentially connected supervisory relay |23 is restored due to re-reversal of talking battery on conductors TI and Ri by the opening of the called party loop circuit and contacts i il are opened and contacts H3 closed to again brightly illuminate the monitor lamp Li@ through the obvious circuit including operated contacts |3| of release delay relay |30. Thus an indication is signaled that the trunk circuit is still seized by the calling line `'although not in the talking condition since the called party has disconnected. When the calling party hangs up and the calling loop circuit to the calling bridge relay |40 is thereby opened, relays |130 and |33 restore to open contacts |3i Vand break the circuit to monitor lamp Lit and cause the lamp to be extinguished thus indicating that the trunk circuit is no longer seized and "is free for seizure by other calling circuits; It is apparent that the trunk circuit being described is under control of the calling party since the restoration of the calling bridge relay |40 when the calling party hangs up is effective to restore contacts lill and |42 to their normal open position and break the called party loop circuit to the supervisory relay I0.

While the monitor signal lamp circuit of the invention has been particularly described in connection with a one-way outgoing dial to dial trunk circuit, it should be understood that the signaling circuit may be applied equally as well to other forms of trunk circuits having a relay operated upon seizure of the circuit and another relay operated when the extension of the call is completed and the calling party answers, with the aforementioned relays having contacts to control the energization of the monitor lamp in a manner to provide bright illumination during seizure and before completion of the call and dim illumination after completion of the call during which the trunk circuit is in talking condition. It should be apparent that a special advantage of this arrangement is a conservation of power since the signal lamp is only dimly illuminated and draws consequent small amounts of current during the comparatively long time when the trunk circuit is in talking condition as contrasted to the short time interval when the trunk circuit is seized and the talking connection is not yet obtained.

Various modifications may be made within the spirit of the invention and the scope of the appended claims.

What I claim is:

l. In a telephone system, the monitor signal lamp arrangement for indicating the operative condition of a trunk circuit including in combination, a source of power, a signal lamp, a resistance, a first circuit including first switch means to connect said lamp directly to said source of power to provide relatively bright illumination, a second circuit including second switch means to connect said lamp to said source of power in series with said resistance to provide relatively dim illumination, first means responsive to seizure of the trunk circuit by a calling line to operate said rst switch means and illuminate said lamp, and second means responsive to the answering by the called line to operate said second switch means to provide relatively dim illumination of said lamp.

2. In a telephone trunk circuit for extending a call from a calling line over a, trunk line to a called line, said trunk circuit having a first relay connected to be operated when said trunk circuit is seized by the connection of the loop circuit of the calling line and a second supervisory relay to be operated when the called line loop circuit is connected over the trunk line and trunk circuit, the monitor signal lamp arrangement for indicating the operative condition of the trunk circuit including in combination, a source oi' power, a signal lamp, a resistance, a rst circuit controlled by the operation of said first re- -lay to be operated to connect said 'lamp directly to said source of power when said rlrst relay is operated to thereby provide relatively bright illu- Vmination of said lamp, and a second circuit con- Vrelatively dim illumination of said lamp.

3. In a1 telephone trunk circuit .for extending a call from a calling line over a trunk line to a called line, said trunk circuit having a first relay connected to be operated when said trunk circuit is seized by the connection of the loop circuit of the calling line and a second supervisory relay to be operated when the called line loop circuit is connected over the trunk line and trunk circuit, the monitor signal lamp arrangement for indicating the operative condition of the trunk circuit including in combination, a source of power, a signal lamp, a resistance, a first circuit including normally open switch contacts of said first relay to be operated to connect said lamp directly to said source of power when said first relay is operated to thereby provide relatively bright illumination of said lamp, said. su-v pervisory relay having normally closed contacts in series with said rst circuit, and a second circuit including normally open switch contacts of said supervisory relay to be operated to connect said lamp in series with said resistance to said source of power when said supervisory relay is operated to thereby provide relatively dim illumination of said lamp, the operation of said supervisory relay to open said normally closed contacts being eiective to break said first circuit connection of said lamp.

No references cited. 

